Battery systems using a thin flexible tape of electrode material have been suggested in the prior art for supplementing or replenishing the supply of anode as well as electrolyte to prolong the life of the battery. An example of a system employing an elongated tape of anode material fed from a supply reel to a take up reel is disclosed in U.S. Pat. No. 4,916,036. The anode described in this patent is supplied from an elongated tape composed of a reactive metal such as lithium wound on a reel and fed from a first chamber through a second reaction chamber containing a solution of electrolyte and cathode to a third chamber in which the tape is wound on a take up reel. The take up reel is driven by a motor under the control of a controller to advance the tape, preferably continuously, through the bath of electrolyte. A continuous fresh supply of anode material is intended to prolong the operation of the battery. Another battery system using a strip of tape containing segments of individual battery cells is taught in U.S. Pat. No. 3,494,796. In this patent each battery cell is composed of its own anode and cathode separated by a layer impregnated with electrolyte. The tape is advanced so that an external pair of collector plate's makes contact with each cell in succession. Thus only one cell at a time is connected to the terminals for heavy discharge while the other cells are held in reserve and discharge at a low level. U.S. Pat. No. 3,577,281 is yet another prior art teaching using an elongated tape coated with an anode material which is driven into a solution of electrolyte.
In a copending application of the joint inventors U.S. Ser. No. 08/231,744 an elongated tape is described containing segmented sections of anode material and/or a source of supplemental electrolyte which is progessively fed into the active electrochemical compartment to control the duration of battery operation. The elongated tape functions as a moving conveyor which is preferably interconnected to form an endless loop. The electrolyte is impregnated into the substrate of the moving conveyor belt.
In accordance with the present invention the moving conveyor, preferably arranged in the form of an endless belt containing impregnated electrolyte, is advanced between an anode and cathode assembly to engage the anode and/or cathode interface surface(s). The anode/electrolyte interface and/or the cathode/electrolyte interface is controlled by the dynamic interaction occuring at the engaging surfaces while simultaneously adjusting the interface spacing to maintain the spacing substantially constant during the elctrochemical reaction. The anode is preferably aluminum or an aluminum alloy although any conventional anode material may be used such as zinc, magnesium, lithium etc. The cathode is preferably an air cathode. The electrolyte is selected for compatibility with the anode material and is preferably impregnated on the moving conveyor as an aqueous medium or in the form of a gel or a microencapsulated composition or is a solid.
It has been discovered in accordance with the present invention that by reacting electrolyte impregnated on a moving conveyor held in physical contact with the surfaces of an anode and cathode structure while maintaining the interface spacing between the anode and cathode surfaces constant it is possible to overcome the problems attributable to electrolyte depletion, surface passivation and oxide build up. As a result of controlling the anode/electrolyte interface and/or the cathode/electrolyte interface in accordance with the present invention by-product build up of dendrite formation, gassing and corrosion are controllable and readily minimized.
The benefits of the present invention will become apparent from the following detailed description of the invention and include extended shelf life, indefinite periods of dormancy under direct operator control, on/off ability, substantially level discharge over the life of the battery with each resumption of electrochemical activity following a period of dormancy occuring at full voltage independent of the period of dormancy and controlled energy densities up to and above 400 k Wh/kg.